Digermenes structure

Four new stable digermenes 66-69 were synthesized from dichlorogermanes and sodium in toluene or lithium naphthalenide (Scheme 10). 66 and 68 have been characterized by X-ray61 (see Section III,B,1). 66-6851 keep their digermene structure in solution, in contrast to 6960 (probably the E isomer due to the steric hindrance in the Z isomer), for which an interconversion with the corresponding germylene was observed. 

For the digermenes, Lappert later reported520 the full crystal structure of R2Ge=GeR2, R = Bsi and a refinement of the tin structure while Masamune has characterized the analog... 

Compound A was obtained from a reaction of tetrakis(2,6-diethylphenyl)digermene with an excess of DMSO in toluene. The molecular structures of both A and B were determined by single-crystal X-ray analyses (Figure 27). 

FIGURE 27. Molecular structure of the oxygenation products A and B of tetrakis(2,6-diisopropylphenyl)digermene (cf. Figure 26). Reprinted with permission from Reference 113. Copyright (1989) American Chemical Society... 

The fraws-bent structure of Ge2H4, the two bridged structures and the germylgermylene structure were found to be real minima. The planar digermene form is the transition state for interconverting the two trans-bent forms. 

X-ray crystallographic analysis of the orange single crystals, which were obtained after the removal of inorganic salts and naphthalene, has revealed that the structure of the orange crystal is that of the digermene ( )-Tbt(Mes)Ge=Ge(Mes)Tbt 10, the dimer of the germylene Tbt(Mes)Ge 2225. The details of the structural analysis of 10 will be discussed later. 

We want to use this knowledge to tell us something about R2M=MR2 and RM=MR, about which we know considerably less. Maybe this information will help chemists make digermenes and distan-nenes that will retain their structures in solution or the gas phase. Maybe it will aid in the synthesis of stable triply bonded compounds of silicon and germanium, or hexasilabenzene ... 

Fig. 10. Interaction diagram for analysis of trans-bending in disilene, digermene, and germasilene. (A) Interaction of the n HOMO and the a orbital of planar doubly bonded structures that is responsible for the trans-bending. (B) Superimposed n and a orbitals from (A) with arrows indicating the stabilizing distortion.

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